ABSTRACT
We report EPR measurements at 9.77 and 34.1 GHz in powder and single crystal samples of the ternary copper amino acid complex Cu(L-arginine)(2)(SO(4)).(H(2)O)(6). The single crystal Electron Paramagnetic Resonance spectra display a single resonance for all magnetic field orientations in the ca and cb crystal planes. In the ab plane they display two resonances for most orientations of the magnetic field, and only one resonance for orientations close to the crystal axes. This behavior is a result of the selective collapse of the resonances corresponding to the four copper sites in the unit cell produced by the exchange interactions between copper ions. From the characteristics of the collapse and the angular dependences of the position and width of the resonances we evaluate the g-tensors of the copper molecules and estimate exchange interactions |J(1)/k(B)|=0.9 K and |J(2)/k(B)|=0.009 K between copper neighbors at 5.908 A and at 15.684 A, respectively. J(1) is assigned to a syn-anti equatorial-apical carboxylate bridge with a total bond length of 7.133 A. J(2) is assigned to a long bridge of 12 atoms with a total bond length of 19.789 A, that includes two hydrogen bonds. The results are discussed in terms of the crystal and electronic structure of Cu(L-arginine)(2)(SO(4)).(H(2)O)(6). We show that J(2) is in excellent agreement with the observed magnetic interaction between the reduced quinone acceptors in the photosynthetic reaction center protein of the bacterium Rb. sphaeroides, which is transmitted along a similar chemical path containing two hydrogen bonds. Our findings indicate that it is valid to estimate values for the exchange interactions between redox centers in proteins transmitted along long chemical paths containing sigma and H-bonds, from data obtained in model systems, and emphasize the importance of measuring exchange interactions in biologically relevant model systems.
Subject(s)
Arginine/chemistry , Copper Sulfate/chemistry , Organometallic Compounds/chemistry , Proteins/chemistry , Crystallography, X-Ray , Electron Spin Resonance Spectroscopy , Hydrogen Bonding , Models, Chemical , Molecular StructureABSTRACT
As plantas denominadas de ruibarbo sintetizam antraquinonas e taninos, que são responsáveis pelos efeitos laxante e adstringente, respectivamente. Análises da qualidade de cinco matérias-primas de ruibarbo foram realizadas a fim de detectar adulterações. As reações para antraquinonas e taninos foram positivas. Os constituintes rapônticos foram observados na amostra de Rheum palmatum (2). As medidas de cinzas totais para Rheum palmatum (2) e Ferraria cathartica estão acima do esperado. Conforme resultados, as amostras de Rheum palmatum (2) e Ferraria cathartica devem estar adulteradas.
Plants known as rhubarb synthesize anthraquinones and tannins. Theses compounds have medicinal uses as laxative and astringent, respectivity. The quality of five raw materials was analysed to detect adulterant. Anthraquinones and tannins reactions were positive. Derivatives rhapontocoside were observed in the sample of Rheum palmatum (2). Total ashes were increased to Rheum palmatum (2) and Ferraria cathartica. According to the results, samples of Rheum palmatum (2) and Ferraria cathartica shoulde are adulterated.
ABSTRACT
Vanillosmopsis erythropappa é um vegetal rico em óleos essenciais, especialmente o á-bisabolol. O objetivo deste estudo foi pesquisar a variação sazonal qualitativa de substâncias naturais, teores de óleos essenciais, cinzas totais, umidade e pH. Os resultados mostraram uma variação de flavonóides, taninos, triterpenóides, esteróides, saponinas, óleos essenciais, cinzas totais, umidade e pH, demonstrando que os aspectos ambientais influenciam o metabolismo dessa espécie. As médias anuais dos valores obtidos foram: óleos essenciais= 0,29 ± 0,09 por cento; cinzas totais= 3,13 ± 0,49 por cento; umidade= 6,56 ± 0,80 por cento e pH= 5,40 ± 0,24.
Vanillosmopsis erythropappa is a plant rich in essential oils, especially á-bisabolol. The aim of this study was research the qualitative seasonal variation of natural substances, tenor of essential oils, total ashes, dampness and pH. The results showed a variation of the flavonoids, tannins, triterpenoids, steroids, saponins, essential oils, total ashes, dampness and pH, demonstrating that environmental aspects influence on the metabolism of this specie. The annual averages of the obtained values were: essential oils = 0,29 ± 0,09 percent; total ashes = 3,13 ± 0,49 percent; dampness= 6,56 ± 0,80 percent and pH = 5,40 ± 0,24.
